today i did a compass experiment that you may find helpful or interesting:i went to a local field near my house, there is a 6'x4" metal picnic bench under a tree.
i set up the p3 on the black top and got a screen shot of the mod values, look at the compass value, it say 1506 if u cant read it!


i then took it to the picnic table whic is all metal, and put the p3 on the right side of it where the metal cross section and legs are, look at the value now, 387!!!



i tried to arm the motors on that spot and they would not arm and i was getting the red compass error notice


i then moved the pe 2' to the left of the picnic table, i was still getting the compass error notice but this was the mod value, 1184. even with the compass error notice, it did arm the motors in that spot as the values were, i suppose acceptable for it. i did take off and flew a little to see if i get any toilet bowl effects or any signs of it going crazy. it flew just fine!!


so i dont know what it means to you, but to me it means:
1-compass is very sensitive
2- if you cant arm the motors, take a look on your compass reading, that may have something to do with it
3- even though by moving the take off point a few feet and getting better values, i would not trust it. i would move more than just a few feet.
4-for this exact reason, i am one of the minotities that does not calibrate compass every flight or every day. in fact ive only done it twice and ive more than 200 flights in all different location, ive travelled 1000 miles away from original calibration spot and did not do a recal.

just passing some info and experiments, thats all.

oh another experiment i did is this,
arm motors and take off manually and then land but dont turn off motors, tried to take off and it wanted to tip over. kill the motors and arm them again and take off, no problems.
here is the link to the video

Wonder why it wouldn't take off ahain after landing??

That's interesting. Where do I look for the compass value?

jayhkr Posted at 2015-8-29 05:12
Wonder why it wouldn't take off ahain after landing??

it does not happen every time but id say around 90% of the time, if i land and not kill motors and then try to take off it does try to flip over, and it can be forwards, backward or to the sides.
as far as why, i have no clue. ive tried a quick thrust up i try gradual but all with same result.
no big deal, unless u go say 2000' down in to a valley and land, if then you kill motors its only going to climb 1650' and no higher!! so ud be kinda SOL.
not that i do it but just as an example where this would be a problem

oksxen Posted at 2015-8-29 05:17
That's interesting. Where do I look for the compass value?

under settings and sensors

I had noticed that same thing when I took off hovered for a minute and landed and then tried to take off again a couple days ago.  I did not understand what was happening but good to know it is not just mine.  I though at first I had a motor going bad.

Thanks for your informative help!

Sir Edward K Posted at 2015-8-29 05:22
I had noticed that same thing when I took off hovered for a minute and landed and then tried to take ...

u er welcome. thats the good part of having a couple of these guys, i use one to test and experiment problems people are having to see if i can find the problem and a fix. for most part i can but certain thing i havent been able to, e.g. thick headedness, lol

I'm not convinced it is on its way to flip over in the video.
I cant see any tendencies like tilting in any direction.

Standing on soft ground like this will surely make the copter tilt slightly while revving the props before lift off, unless it is perfectly leveled, I think.

What if you don't take of as quickly after restarting the motors, will it not lift one side slightly before the other side, then too?

aek Posted at 2015-8-29 05:35
I'm not convinced it is on its way to flip over in the video.
I cant see any tendencies like tilting ...

i know it really is not visible in video and it does it on hard top too. i actually have a video of the flip i did on grass, it was intentional for testing purposes. i noticed this a while back and today i actually went to test the theory. i ll try to find the clip of the flip

aek Posted at 2015-8-29 05:35
I'm not convinced it is on its way to flip over in the video.
I cant see any tendencies like tilting ...

if u start the motors and let it sit there, for as long as u want, when u go to take off manually, it takes off with no problem. the problem is only when u land whether on hard or soft surface and u dont kill the motors and then try to take off. whether u apply quick throttle or gradual, all same result, flipover, forwards or backwards or sideways, no real pattern

aek Posted at 2015-8-29 05:35
I'm not convinced it is on its way to flip over in the video.
I cant see any tendencies like tilting ...

here is the clip better shows the p3 trying to flip.

aek Posted at 2015-8-28 16:35
I'm not convinced it is on its way to flip over in the video.
I cant see any tendencies like tilting ...

I noticed this a few days ago and made me hesitant to fly.  So to verify I went out on my flat driveway and took off hovered for 20 seconds landed without killing motors but enough they would idle.  Then slowly tried to take off.  Mine tipped backwards lifting front feet off the driveway leaving back feet planted.  I took video while doing this but it is hard to see.  So I will charge my gopro and tomorrow I will get it from the side at ground level so you can see it.  It happens EVERY TIME you do it in this sequence.  It is repeatable.

rayrokni Posted at 2015-8-28 18:08
here is the clip better shows the p3 trying to flip.

...

I tried this with same result. I then disabled VPS with rotors off, then restarted and took off, landed, took off again without stopping rotors and it worked fine.  I then tried landing again with VPS on, tried turning off VPS with rotors still turning on the ground and it jumped dramatically trying to tip over. Shut rotors down quickly to keep it from tipping over. So it appears it may be a VPS related issue. Bottomline, shut down the rotors when you land if using VPS.

sww60 Posted at 2015-8-29 07:50
I tried this with same result. I then disabled VPS with rotors off, then restarted and took off, la ...

i will do the same and report back, if it does the same on mine too then u r probably right.
thanks for that info.

glad i read this thread before i'm in this situation.
does this happen with any firmware version?

radius Posted at 2015-8-29 13:47
glad i read this thread before i'm in this situation.
does this happen with any firmware version?

I will try it on fw 126 and report

rayrokni Posted at 2015-8-29 02:19
i will do the same and report back, if it does the same on mine too then u r probably right.
thank ...

Hi Ray. Your are right I have exp. the same happening to me. I have the opinion that it have to do
with the VPS. It seems not to opperate well on grass and rough concrete and bouth of your video
is on these surfaces. Happy playing.

Awesome info Ray, thanks.  I don't calibrate the compass before each flight anymore.  Instead, I check the sensors and if they are good to go I takeoff.  No problems so far.  I think the issue you discovered, tip-over, during takeoff after landing is VPS related.  I experienced the same issues and now shut down after each landing.

PS. You should be working for DJI.  Be great if DJI is watching and making corrections.

Joe Blow Posted at 2015-8-29 20:32
Awesome info Ray, thanks.  I don't calibrate the compass before each flight anymore.  Instead, I che ...

i dont play well with others, thats why ive always worked for myself. i just enjoy this so much i actually repaired one for some guy from virginia. he said he found me from the forum!!!
it was a stuck fw issue!!!

louis.lowveldlu Posted at 2015-8-29 06:51
Hi Ray. Your are right I have exp. the same happening to me. I have the opinion that it have to do ...

Here is video showing the problem taking off from my driveway.  Not grass or rough concrete.  It does appear to be VPS problem.

Sir Edward K Posted at 2015-8-29 21:24
Here is video showing the problem taking off from my driveway.  Not grass or rough concrete.  It d ...

exactly what i was trying to show but didnt have a tripod, lol.
now turn off vps and see if that issue goes away

rayrokni Posted at 2015-8-29 08:37
exactly what i was trying to show but didnt have a tripod, lol.
now turn off vps and see if that i ...

Alright rayrokni, Here is video with VPS Turned off.   And as you can see I can hover land and re-take off.  But you can sure tell the difference (without VPS). lol

Sorry it is not adding video.  Trying again

Sir Edward K Posted at 2015-8-29 22:21
Alright rayrokni, Here is video with VPS Turned off.   And as you can see I can hover land and re-t ...

Great thanks, I will try also later today. Btw you can call me, Sir ray, if u like! Lol

rayrokni Posted at 2015-8-29 09:37
Great thanks, I will try also later today. Btw you can call me, Sir ray, if u like! Lol

Sir Edward K is an inside joke with my kids (who are now grown and out of the house).
como desee Sir Ray

Sir Edward K Posted at 2015-8-29 22:43
Sir Edward K is an inside joke with my kids (who are now grown and out of the house).
como desee S ...

Me Puede llamar como quiera

That is really nothing new at all, most ppl know this since the phantom1. The same will happen when you place the phantom on a table inside your house etc. I have several places indoor with total different mod values, for example the kitchen hotplate. Its normal that the compass reacts to any metal

Daninho Posted at 2015-8-29 10:39
That is really nothing new at all, most ppl know this since the phantom1. The same will happen when  ...

Yes, that was his point.  To show  others how the mod values differ and why you should check them.  It was meant for users like me.  who just started flying.

Daninho Posted at 2015-8-29 23:39
That is really nothing new at all, most ppl know this since the phantom1. The same will happen when  ...

...and I'm sure you knew this the first day you investigated a Phantom1, huh...because you are all-knowing?    Arrogance....



Sir Ray....thank you for the real life, empirical data!

Sir Edward K Posted at 2015-8-29 10:43
Sir Edward K is an inside joke with my kids (who are now grown and out of the house).
como desee S ...

Inside joke - is that anywhere near the same as a play on words?

My stepson's truck broke down the other day - he's in the Army in El Paso (our army!).
The company who came to tow his vehicle has the dubious name of:

Kamel Towing

LOL

aburkefl@gmail. Posted at 2015-8-29 14:15
Inside joke - is that anywhere near the same as a play on words?

My stepson's truck broke down th ...

Kamel Towing LOL  for real?  

Daninho Posted at 2015-8-29 23:39
That is really nothing new at all, most ppl know this since the phantom1. The same will happen when  ...

so whats ur point? it may be well known to you and some, ok. so the rest should just know?

Flight Raptor Posted at 2015-8-30 02:57
...and I'm sure you knew this the first day you investigated a Phantom1, huh...because you are all- ...

you are most welcome. i just dont get some ppl.  i gotta get my ignore button again, cuz i just cant keep my temper under control when it comes to arrogance.

thanks

Sir Edward K Posted at 2015-8-30 02:50
Yes, that was his point.  To show  others how the mod values differ and why you should check them. ...

hit "ignore"!, anyways i did turn off vps and now it lands and takes off fine without having to kill motors first.
puzzle, solved!!!
thanks

rayrokni Posted at 2015-8-30 11:09
hit "ignore"!, anyways i did turn off vps and now it lands and takes off fine without having to ki ...

Hey rayrokni, Im wondering if you have any suggestions mu phantom 3 p gives me teh red yellow compass crap all the time, i can be almost naked miles in a 60 acre field my girl holds the remote about 100 yards from me and tells me waht its saying and icant seem to calibrate the compass - eachtime it fails due to electormagnetic interference. The compass mod is never above 1100 so waht does one do to reset the dam thing? any suggestions appreciated. how do i getit back up to 1500 when in conditions and environment it should be?
Thanks!

Kookaburra Posted at 2015-9-3 07:30
Hey rayrokni, Im wondering if you have any suggestions mu phantom 3 p gives me teh red yellow comp ...

its because you are in the "land under".LOL
the range here in the northern hemisphere is supposed to be between 1400 to 1600. when i go to calibrate my compass, which i have only done once when out of the box and then once after FW update. I DO NOT recalibrate compass every flight or day. i check the mod value, looking for 1400-1600 and also do a quick manual compass chk.
anyways, how i calibrate compass:
like you, barely dressed, no watches, cell phones , jewelry, belt buckles etc.
leave my car 50' away
LEAVE RC AND DEVICE NEAR THE CAR, you dont need it with you to cal compass. inititae it and then walk to your p3 30' away, and i do the compass dance instead of twisting the p3 around.
another trick u may want to try: use a manual compass and find north, draw a line on whatever so u know where north is. position the nose of p3 on that line. so basically your body and the way u hold the p3 nose should align with north, then do the compass dance.

let me know if any of this makes sense, if not i can call u, speaking easier than typing.

BTW, the compass is in the bottom right of the landing gear, under the 2 small screws. so r u wearing any jewelry on that hand when calibrating compass.

Thanks very much for this advice - I want to get this baby going with but more reliance it wont crash especially as i want to flyover sand and water. Ill let you know how i get on
Thanks again from the land down under!

people keep saying when they land they sometimes get a compass error. well it is quite possible if u land where there is interference, metal objects, concrete has metal rebars, decks have metal hangers unerneath, etc etc. it happens to me too. i just move it sometimes as little as 1' and error goes away. just trust the machine, if it tells you compass error, it doesnt mean there is an actual problem that cant be fixed or that compass is broke!!! it means move the ..... thing. lol

That was time well spent folks. Greetings, and thanks for a bunch of useful relevant input and data - Yeah, I noticed the oddball who forgot that there's first time pilots, forum etiquette and plain ol' being a good sport. Glad we appear to be mature enough not to lose 'the rag'.
A thought was occurring whilst reading - Could switching from P to A or F knock out the issue without having to shut down the engines. Apologies - no possible now, or I'd post results. Just a thought. LOL